This invention relates to the catalytic conversion of hydrocarbons and the regeneration of catalyst particles used in a sequence of two stage regeneration as a means for restricting combustion temperatues encountered during the removal of carbonaceous deposits of hydrocarbon conversion. In a particular aspect the present invention is concerned with a low profile catalytic cracking-catalyst regeneration system which effectively achieves a rapid separation of formed suspension within a restricted and desired time frame of operation.
The prior art is full of many different arrangements of vessels for achieving the catalytic conversion of oil feeds and regeneration of catalyst employed. Many of these system arrangements perform particularly desired operating functions peculiar to the operation and concept of invention contemplated. With the development of high activity zeolite cracking catalyst and variations thereon depending on the crystal structure employed as well as the hydrocarbon feed to be converted there has been a need to develop some particular apparatus arrangements for some particular conversion operations. In most of these operations there is a need to limit hydrocarbon conversion time and temperature in a riser hydrocarbon conversion zone and limit the temperature of the regeneration operation to avoid damage to the catalyst. Various techniques have been employed in the prior art to accomplish each of these ends.
Palmer etal U.S. Pat. No. 3,123,547 discloses an expanding riser reaction tube of more restricted dimensions at its discharge end where the suspension is passed through slotted openings in the riser wall.
Haddad etal U.S. Pat. No. 4,219,407 discharges a suspension from a riser by radially extending arms of inverted channels which curve downward at the outer extremity thereof.
Heffley etal U.S. Pat. No. 4,173,527 discharges a suspension from a riser by first centrifugally spinning the suspension so that centrifugally separated solids pass outside a smaller diameter vapor withdrawal pipe coaxially aligned with the riser outlet.
Stine etal U.S. Pat. No. 3,838,036 and many others discharge a hydrocarbon-catalyst suspension from a conversion zone directly into cyclone separation zones. Numerous other patents in the prior art such as Vermilion Jr. U.S. Pat. No. 4,064,038 and Owen U.S. Pat. No. 3,886,060 also discharge directly into cyclones from riser contact zones.
Greensfelder etal U.S. Pat. No. 2,398,739 discloses two stage dense fluid catalyst bed regeneration in a side-by-side arrangement.
Thomas etal U.S. Pat. No. 2,414,002 discloses a dense phase catalyst upflow regeneration operation followed by a more dense catalyst phase downflow regeneration zone. Other two stage regeneration arrangements of the prior art include Jahnig U.S. Pat. No. 2,434,567, Jewell U.S. Pat. No. 2,882,218; Rowe 4,388,218; Dean etal U.S. Pat. ;b 4,332,674; Pfeiffer etal U.S. Pat. No. 3,563,911; Luckenbach U.S. Pat. No. 3,902,990 and Luckenbach U.S. Pat. No. 4,176,084 among many others.
The present invention is concerned with a unique technique for separating a suspension discharged from a riser conversion or regeneration zone. The present invention is also concerned with a unique technique for effecting two stage regeneration of catalyst particles in temperature controlled atmospheres whereby hydrocarbonaceous deposits may be removed to a desired low residual coke level for recycle to a hydrocarbon conversion zone.
It is recognized at this stage of the petroleum refining industry that heavy oils such as residual portions of crude oils and reduced crudes boiling above 650.degree. F. comprising Conradson carbon producing components including asphaltenes and porphyrins boiling above about 1025.degree. F. are less than desirable charge stocks in a normal gas oil catalytic cracking operation because the Conradson carbon producing components and metal contaminants rapidly reduce the catalyst cracking activity and selectivity as well as cause undesired yields of dry gas and coke at the expense of desired gasoline boiling range products.
Crude oils comprising metallo-organic compounds are known in which from 30 to 60 percent or more by volume comprise compounds boiling above about 650.degree. F. with from about 10 to 30 volume percent of the total crude volume comprising compounds boiling above about 1025.degree. F. or 1050.degree. F. at atmospheric pressure. Because of the scarcity of high quality gas oils boiling in the range of 650.degree. F. up to about 1025.degree. F., it is now necessary to develop economical and efficient processes for converting residual oils, reduced crudes and more of the crude barrel to desired products of gasoline, gasoline precursors and light fuel oils.
It is also important economically to be able to employ existing processing equipment such as gas oil fluid catalytic cracking processing equipment for converting the less desirable residual oil feed stocks in the absence of major modification and reconstruction of existing equipment. That is, it is particularly desirable to offset the destructive effects of metal contaminants and high Conradson carbon feeds by employing some modified processing parameters rather than effecting major equipment changes. More important is the need to achieve conversion of more of the crude barrel to gasoline and gasoline precursors than obtainable with a more clean gas oil feed as accomplished in existing fluid catalytic cracking (FCC) operations.
Crude oils in the natural state contain a variety of metalloorganic compounds which contribute to undesirable catalyst functions in cracking the heaviest or resid portion of a crude oil. Among these compounds are coke precursors (asphaltenes, poly-nuclear aromatics of at least 5 rings); heavy metals such as iron, nickel, vanadium and copper as free metals, oxides and sulfides or combined as porphyrins in combination with deactivating amounts of sodium, potassium, sulfur and nitrogen materials. Materials such as high boiling asphaltenes tend to break down into coke during the cracking operation which deposits on the catalyst as carbonaceous or hydrocarbonaceous material thereby inactivating the catalyst cracking activity and particularly its selectivity. Metal deposits further contribute to this inactivation of catalyst particles beyond simple restoration techniques and such metals deposition can cause terminal deactivation of a crystalline zeolite structure employed in a cracking catalyst. It has been determined that the heavy metals transfer almost quantitively from the feed stock to a catalyst particle surface.
Numerous proposals are provided in the prior art for upgrading poor quality residual oil feeds to obtain desired gasoline products. These proposals include the combination of one or more of vacuum distillation solvent extraction, hydrotreating, thermal visbreaking in combination with catalytic cracking and combinations thereof, all of which are criticized as economically unattractive for processing high cost crude oil and particularly that of poor quality.
A number of patents in the prior art disclose the concept of passivating metal contaminants of nickel, vanadium, copper and iron by the addition of metals and compounds thereof selected from the group of magnesium, calcium, strontium, barium, scandium, titanium, chromium, molybdenium, manganese, cobalt, antimony, zinc, cadmium, zirconium, tin, lead and rare earth metals, all of which may or may not contribute to altering product selectivityy in a fluid catalytic cracking operation.
It is clear from the above that innovative if not dramatic processing contributions are desperately needed at this stage of the petroleum refining industry. The present invention is directed to a new and novel combination of fluid catalytic cracking processing restrictions and operating parameters which amount to a giant step forward in the catalytic conversion of reduced crudes to gasoline, gasoline precursors and higher boiling liquids and reducing problems associated with the production of gasoline, fuel oils and gasoline precursors from poor quality crudes.
The present invention further addressed itself to obtaining an efficient and economically attractive heat balanced operation for upgrading poor quality crude oils comprising residual portions of crude oils including atmospheric gas oils and higher boiling portions thereof known as vacuum gas oils and vacuum resid boiling above about 1025.degree. F. to produce gasoline and other useful products. The present invention is also directed to a combination of operating parameters by which the catalyst operating life is retained for an extended on-stream life during conversion of poor quality residual oils comprising components boiling above 1025.degree. F.